1. Field of the Invention
The present invention relates to an image forming apparatus such as a printer, copier, and facsimile.
2. Description of a Related Art
As a color image forming apparatus, an apparatus for forming an image by a rotary developer unit having developing units of four colors of yellow, magenta, cyan, and black is known. Since the image forming apparatus of this type forms a color image by rotating the rotary developer unit to develop the image of the respective colors, other component parts such as a transfer device are disposed around the rotary developer unit (see JP-A-8-328348, JP-A-2001-175077, and JP-A-2002-341706).
However, when the exit position of a beam for writing a latent image onto an image carrier is approximated to the rotary developer unit in order to miniaturize the image forming apparatus, since the optical path is obstructed by the rotary developer unit, sometimes there is no choice but to make the incident angle of the beam on the image carrier larger relative to the normal line of the image carrier. Thus, if the incident angle of the beam on the image carrier becomes larger relative to the normal line of the image carrier, optical path shift due to manufacturing variations becomes easier to be produced, and, as a result, image defects are produced. In addition, a problem that the energy loss of the beam becomes larger sometimes arises.
Further, in the case where an exposure device is disposed below the rotary developer unit and the beam is output upwardly from the exposure device, sometimes the toner adheres to the exit portion of the beam and the image is disturbed.